The work in this project mainly relates to problems in optical imaging and other uses of lasers as non-invasive probes of biological media. Applications in optical imaging require being able to distinguish between regions in tissue that differ from normal tissue either because of different absorption or scattering properties. This means that photons are either more likely to be absorbed in these regions, or tend to move in or out of the regions at a rate differing from their motion in normal tissue. The notion of the continuous-time random walk has been applied to study such questions for photon transport in tissue and produces exact rather than approximate results for physically interesting quantities. Earlier studies of regions with enhanced absorption have made use of an approximation in which the abnormality is modelled as a single point in the tissue to understand how the reflection or transmission of light is affected. A study to determine how these properties are changed when the anomalous region consists of several points has been used to indicate when the behavior of detected light might will change with an increased number of scattering points. The mathematical tool used in this study is based on the theory of random walks. The analysis was carried out in collaboration with Dr. A. Gandjbakhche (NICHD).